Various gauges, devices, systems and techniques have been utilized, in the prior art, to measure the various optical dimensions of lenses. Typical of such devices is the Geneva gauge for measuring spherical surface curvatures in diopter units. In the precision optical industry, spherometers of higher accuracy are required for gauging the radius of curvature. However, such spherometers have the drawback that charts are required to convert sagittal depth measurements into radius of curvature measurements, or diopters.
Attempts to improve on this technology have included the development of a compensated diopter gauge, such as disclosed in U.S. Pat. No. 3,861,048-Thompson. In that patent, a diopter gauge having a large scale and associated indicator needle is provided, one diopter being indicated by each complete revolution of the indicator needle. A compensating scale is associated with the large scale and indicator needle, such that the indicator needle may be set to compensate for the linearity error of the sagittal depth measurements versus diopters, and so that the sagittal measurement scale is actually reading diopters. The measurement technique disclosed in the aforementioned U.S. patent comprises the following steps: (1) place a flat lens on a contact ring, (2) zero out the gauge, (3) replace the flat lens with a lens to be measured, and (4) read the sagittal depth measurement, in diopters, on the gauge.
Further drawbacks of an arrangement such as disclosed in the Thompson patent are evident. Thompson does not disclose a gauge for digitally measuring the sagittal depth of a lens. Thus, a precise numerical measurement is not displayed. In addition, the Thompson gauge is a very simple, single-measurement gauge in that it only measures sagittal depth. There is no provision, in the Thompson gauge, for the additional measurement of lens thickness. Thus, such a gauge does not provide a convenient means for measuring all the lens dimensions typically employed in lens fabrication procedures, and is also not amenable to being employed in an automated (data processor) system.
A second arrangement of the prior art, disclosed in U.S. Pat. No. 2,646,627-Tillyer et al, comprises a thickness gauge for lenses. However, such an arrangement is quite similar to the gauge disclosed in the previously discussed patent, in that the thickness gauge of Tillyer et al comprises a strictly mechanical gauge, and thus does not numerically display (via a digital display) the thickness of the lens. In addition, as is the case with the previous patent, this patent discloses a thickness gauge which is not amenable to being employed in an automated (data processing) system. Finally, the thickness gauge of Tillyer et al comprises a mere single-measurement gauge.
A further prior art arrangement disclosed in U.S. Pat. No. 4,205,452-Wichterle et al, relates to a dual-measurement gauge, that is, a measuring set for determination of the sagittal depth and the average central curvature of contact lenses. However, the arrangement of this patent merely provides an analog device for measuring and indicating the sagittal depth and central curvature of the lens. Thus, the precision normally associated with digital measuring instruments is not provided by the arrangement of Wichterle et al. In addition, the arrangement of Wichterle et al, and the associated technique of measuring, require searching back and forth between the various measuring units, as well as multiple operator motions in connection with movement of the lens in order to obtain the desired measurements.